The Wagnerites turned out in force at the Art Museum on Saturday for “Tristan und Isolde,” live from the Met in HD broadcast. It starred soprano Deborah Voigt and tenor Robert Dean Smith – her fourth Tristan in as many performances; Ben Heppner’s illness has required considerable ingenuity in procuring replacements for a difficult-to-cast role.

For someone making his Met debut before a worldwide audience with no rehearsal, Smith was remarkably at ease, and sounded terrific. Mezzo-soprano Michelle DeYoung was a caring Brangaene, and her singing was luscious throughout.

Voigt has had cosmetic surgery as well as her celebrated gastric bypass, and at times her face was oddly expressionless and masklike. She got past some early intonation issues to deliver the goods for virtually all of this Big Sing, only to go flat on the final note. No doubt that will be fixed by the time the performance goes to PBS and DVD, but it was heartbreaking at the time.

Baritone Eike Wilm Schulte was a superb Kurwenal; it may be time for bass Matti Salminen to consider stepping down from King Marke’s throne.

Conductor James Levine simply inhabited the score; his conducting was just about flawless. He also gave a rare interview to guest host Susan Graham, who is to the TV-newsie manner born.

This broadcast came with an innovation: multiple images – up to six at a time, which let viewers choose whether to look at the big picture or at close-ups. It was sometimes effective, but more often annoying, yanking the audience out of the spell of Wagner’s music. It did, however, serve to obscure some of the less felicitous aspects of Deiter Dorn’s staging.

In its first HD outings, the Art Museum had a persistent problem with wanderers — whether latecomers or those who go in and out during the performance — wrecking the picture with exterior light coming through the center doors. They’ve now fixed that by the simple expedient of closing the center doors and opening the side doors.

And there was great rejoicing.